Wales international Lewis Price signed a two-year deal with Millers during the close season after leaving South Yorkshire neighbours Sheffield Wednesday.
The experienced stopper will provide stiff competition to current number one Lee Camp, after many years playing in the second tier of English football.
Price started his career with Ipswich Town but after four years at Portman Road he left for Derby County where he played alongside current boss Alan Stubbs.
Spells at Crystal Palace and Sheffield Wednesday followed, where he helped the latter to the Play-off final in 2016.
Price has 11 caps for Wales after making his debut in 2005.